I regret this decision but at the same time I respect it.
Adding manually has an inconvenient for users, it does not permit to set up the search suggestions.
How would you recommend that this should be solved? making this settable in the edition dialog?

In D13673#281629, @jcimalando wrote:

I regret this decision but at the same time I respect it.
Adding manually has an inconvenient for users, it does not permit to set up the search suggestions.

It would, if Bing supported OpenSearch as other search engines.

How would you recommend that this should be solved? making this settable in the edition dialog?

No, I don't see a reason to add another default search engine. Currently, there is: the most used one (Google), two privacy oriented engines (StartPage + DuckDuckGo) and Wikipedia.